Women's bodies have become part of the terrain of conflict, according to a new report by Amnesty International.

Rape and sexual abuse are not just a by-product of war but are used as a deliberate military strategy, it says.

The opportunistic rape and pillage of previous centuries has been replaced in modern conflict by rape used as an orchestrated combat tool.

And while Amnesty cites ongoing conflicts in Colombia, Iraq, Sudan, Chechnya, Nepal and Afghanistan, the use of rape as a weapon of war goes back much further.

Spoils of war?

From the systematic rape of women in Bosnia, to an estimated 200,000 women raped during the battle for Bangladeshi independence in 1971, to Japanese rapes during the 1937 occupation of Nanking - the past century offers too many examples.

Gita Sahgal, of Amnesty International, told the BBC News website it was a mistake to think such assaults were primarily about the age-old "spoils of war", or sexual gratification.

Rape is often used in ethnic conflicts as a way for attackers to perpetuate their social control and redraw ethnic boundaries, she said.

"Women are seen as the reproducers and carers of the community," she said.

Women were raped so they could give birth to a Serbian baby

Medecins Sans Frontieres report

"Therefore if one group wants to control another they often do it by impregnating women of the other community because they see it as a way of destroying the opposing community."

A report by Medecins Sans Frontieres says it first came across rape as a weapon in the 1990s.

"In Bosnia systematic rape was used as part of the strategy of ethnic cleansing," it said.

"Women were raped so they could give birth to a Serbian baby."

The same tactic was used in a "very strategic attack" by state-backed Pakistani troops during the fight for Bangladesh's independence in 1971, Ms Sahgal said.

Ex-"comfort women" in Korea hold a weekly rally demanding reparations

"They were saying 'we will make you breed Punjabi children'," she said, with the aim of weakening the integrity of the opposing ethnic group.

Amnesty this year accused the pro-government Janjaweed militias in Sudan's Darfur region of using mass rape in order to punish, humiliate and control non-Arab groups.

Such attacks cause women and children to flee their homes, lead to fragmentation of communities and bring the risk of infection with HIV/Aids.

Sexual violence is also used to destabilise communities and sow terror, Amnesty says in its Lives Blown Apart report.

In Colombia, rival groups rape, mutilate and kill women and girls in order to impose "punitive codes of conduct on entire towns and villages", so strengthening their control.

Act with impunity

The strategic use of rape in war is not a new phenomenon but only recently has it begun to be documented, chiefly in the Democratic Republic of Congo, Colombia and Sudan, said Ms Sahgal.

And even after conflicts are resolved, few countries seem willing to tackle what is often seen as a crime against individual women rather than a strategy of war.

In many nations the collapse of the rule of law leaves them unable to deal with allegations of rape, while in others women feel too exposed to stigma to accuse their attackers.

International courts have tackled some cases in Bosnia, where Muslim women were forced into sexual slavery in the town of Foca in the 1990s, and in Rwanda, but the vast majority of perpetrators act with impunity.

Women's lives and their bodies have been the unacknowledged casualties of war for too long

Amnesty's Lives Blown Apart report

Representatives of the 200,000 "comfort women" forcibly drafted into military sexual slavery by Japan from 1928 until the end of World War II are still fighting for restitution.

Far from colluding, women from Korea, China, Taiwan, the Philippines, Malaysia and East Timor were "severely coerced" into prostitution, says Ms Sahgal.

And whether a woman is raped at gunpoint or trafficked into sexual slavery by an occupying force, the sexual abuse will shape not just her own but her community's future for years to come.

"Survivors face emotional torment, psychological damage, physical injuries, disease, social ostracism and many other consequences that can devastate their lives," says Amnesty.

"Women's lives and their bodies have been the unacknowledged casualties of war for too long."